https://www.alzheimers.org.uk/about-dementia/is-dementia-hereditary
Can Alzheimer’s disease be inherited?
In the vast majority of cases (more than 99 in 100), Alzheimer’s disease is not inherited.
The most important risk factor for Alzheimer's disease is age. Because Alzheimer's disease is so common in people in their late 70s and 80s, having a parent or grandparent with Alzheimer's disease at this age does not change your risk compared to the rest of the population.
However, if somebody has developed Alzheimer’s disease at an earlier age (for example, less than 60 years-old) there is a greater chance that it may be a type of Alzheimer’s disease that can be passed on.